Reconfigurable Control Scheme Research Articles

Reconfigurable supply-based feedback control for enhanced energy flexibility of air-conditioning systems facilitating grid-interactive buildings

Air-conditioning systems have great potential to provide energy flexibility services to the power grids of high-renewable penetration, due to their high power consumption and inherent energy flexibilities. Direct load control by switching off some operating chillers is the simplest and effective means for air-conditioning systems in buildings to respond to urgent power reduction requests of power grids. However, the implementation of this approach in today's buildings, which widely adopt demand-based feedback controls, would result in serious problems including disordered cooling distribution and likely extra energy consumption. This study, therefore, proposes a reconfigurable control strategy to address these problems. This strategy consists of supply-based feedback control, incorporated with the conventional demand-based feedback control, a control loop reconfiguration scheme and a setpoint reset scheme, facilitating effective control under limited cooling supply and smooth transition between supply-based and demand-based feedback control modes. The proposed control strategy is deployed in a commonly-used digital controller to conduct hardware-in-the-loop control tests on an air-conditioning system involving six AHUs. Test results show that the reconfigurable control achieves commendable control performance. Proper chilled water distribution enables even thermal comfort control among the building zones during demand response and rebound periods. Temperature deviation of the building zones is controlled below 0.2 K most of the time. 11.6 % and 27 % of power demand reductions are achieved during demand response and rebound periods respectively, using the proposed reconfigurable control compared with that using conventional controls.

Distributed Fault-Tolerant Formation Tracking Control for Multiagent Systems With Multiple Leaders and Constrained Actuators.

The distributed formation tracking control problem with multiple leaders under actuator faults and constraints is investigated in this article. All followers in the multiagent system should achieve a desired time-varying formation and track the convex combination of multiple leaders. To accomplish the control task, an active reconfigurable control scheme is proposed using the local information between agents, as well as the fault values of individuals provided by fault estimation observers. Combining with the Lyapunov stability theorem and the property of the Laplacian matrix, the control gains are calculated using the adaptive technique with a formation tracking feasibility condition. The original reconfigurable protocol is modified by utilizing anti-windup compensators to against saturation phenomenons (both magnitude and rate) in actuators. The simulation results validate that the presented scheme can address the faults as well as the actuator saturation.

Autonomous Attitude Reconstruction Analysis for Propulsion System with Typical Thrust Drop Fault

The propulsion system is one of the important and vulnerable sub-systems in a strap-on launch vehicle. Among different failure modes, the thrust drop fault is the most common and remediable one. It degrades vehicle attitude tracking ability directly. To this end, this paper focuses on the design and application of attitude reconstruction problems with a thrust loss fault during the ascending flight phase. We firstly analyze the special failure modes and impacts on the propulsion system through a Failure Modes and Effects Analysis (FMEA). Then, six degrees of freedom dynamic and kinematic models are formulated, which are integrated into the Matlab/Simulink environment afterward. The above models’ validation is realized through numerical simulations with different fault severity. Simulation results show that the max attitude deviation is only 0.67° approximately in the pitch angle channel under normal conditions, and the flight attitude angle deviation is directly proportional to the thrust loss percentage when the thrust drop fault occurs. Based on the validated models, a practical reconfigurable ideal through adjusting the control allocation matrix is analyzed. Then, an automation redistribution mechanism based on the moment equivalent principle before and after the thrust drop is proposed to realize proportional allocation of virtual control command among the actuators. The effectiveness of the designed attitude reconstruction method is demonstrated through numerical simulations and comparison analysis under various fault scenarios. The results show that the rocket attitude can be quickly adjusted to the predetermined program angle within about 2.5 s after the shutdown failure of a single engine, and the flight speed and altitude can also reach the required value with another 17 s engine operation. Therefore, the designed control reconfiguration strategy can deal with the thrust loss fault with high practicability and can be applied to real-time FTC systems. Last but not least, conclusions and prospects are presented to inspire researchers with further exploration in this field.

Distributed control reconfiguration of nonlinear interconnected systems in the presence of actuator faults

AbstractThis article proposes a new method of distributed fault‐tolerant control for a class of nonlinear interconnected systems with actuator faults. This method is based on fault‐hiding idea as a reconfiguration control scheme and tries to redesign the control signal according to the dynamics of the faulty subsystem. Based on fault‐hiding principle, after diagnosing actuator faults, control signals are modified by a predesigned dynamic block which is implemented in the closed‐loop control structure with the same nominal controller. Subsystems are considered as nonlinear Lipschitz systems which interact with each other through nonlinear interconnection dynamics. Because of interactions, occurring a fault in one subsystem causes instability in the overall large‐scale system. A distributed control scheme based on solving a new linear matrix inequality is presented to obtain the control inputs so that it can recover stability and performance of the overall system. Simulation results illustrate and verify the effectiveness of the proposed control approach.

Integrated active fault‐tolerant formation control for networked multi‐agent systems

This paper focuses on the design and simulation of an integrated reconfigurable control strategy for networked multi-agent systems. The control task is to remain the desired time-varying formation in the presence of actuator faults, and to well address the pairing between fault estimation and reconfigurable formation control. A decentralized fault estimation method using observer based estimator is presented to estimate both additive and multiplicative fault values. The reconfigurable control is constructed by adaptive technique using a distributed strategy. Only the information from neighboring agents as well as the fault values are required. The adaptive gains and fault estimates are designed by analyzing the Lyapunov stability of the overall system. The simulation results validate that the proposed integrated fault-tolerant formation control scheme can recover the original desired formation if there are faulty agents in system.

A multi-model based adaptive reconfiguration control scheme for an electro-hydraulic position servo system

A multi-model based adaptive reconfiguration control scheme for an electro-hydraulic position servo system

Reconfigurable-Based Fault-Tolerant Control for Continuous-Time Markov Jump Piecewise-Affine Systems with Allowable Switching Paths

In this paper, the reconfigurable control design problem is studied for a class of continuous-time Markov jump piecewise-affine (PWA) systems with sensor and actuator faults. A reconfiguration block is designed to recover mean-square input-to-state stability (ISS) of the faulty closed-loop system under virtual sensor and virtual actuator. Then, a novel algorithm for computing all the allowable switching paths (ASPs) is developed to overcome the issues of redundant empty paths and mismatch regions, and a S-procedure with the ellipsoidal outer approximation estimation is employed to cope with the affine term. Furthermore, a nonlinear approximation is introduced using the PWA technique to approximate the faulty Markov jump nonlinear systems. Finally, one example is illustrated to demonstrate the effectiveness and advantages of the designed reconfigurable control strategy with an ASPs algorithm.

A Secondary Reconfigurable Inverter and Its Control Strategy

This article proposes a topology of the secondary reconfigurable inverter and the corresponding fault-tolerant control strategy. When the secondary reconfigurable inverter is operating normally, its topology structure is the TPSS circuit. When the power semiconductor devices in the inverter are faulty, the inverter circuit needs to be reconfigured. After removing the faulty power semiconductor devices, the remaining power semiconductor devices and the DC side powers are reconstructed as the TPFS structure to keep the system running normally. This article also proposes a switch-pulse-resetting algorithm. This paper adopts the control strategy connecting the constant-voltage, constant-frequency control method with the switch pulse resetting algorithm. It need not change the control algorithm when the proposed reconfigurable inverter is transformed from the normal running state into the faulty running state. The inverter dependability is greatly improved. Finally, the feasibility and effectiveness of the proposed second reconfigurable inverter topology and control strategy are verified by simulation and experiment.

Distributed MPC for Reconfigurable Architecture Systems via Alternating Direction Method of Multipliers

This paper investigates the distributed model predictive control (MPC) problem of linear systems where the network topology is changeable by the way of inserting new subsystems, disconnecting existing subsystems, or merely modifying the couplings between different subsystems. To equip live systems with a quick response ability when modifying network topology, while keeping a satisfactory dynamic performance, a novel reconfiguration control scheme based on the alternating direction method of multipliers (ADMM) is presented. In this scheme, the local controllers directly influenced by the structure realignment are redesigned in the reconfiguration control. Meanwhile, by employing the powerful ADMM algorithm, the iterative formulas for solving the reconfigured optimization problem are obtained, which significantly accelerate the computation speed and ensure a timely output of the reconfigured optimal control response. Ultimately, the presented reconfiguration scheme is applied to the level control of a benchmark four-tank plant to illustrate its effectiveness and main characteristics.

Reconfigurable Model Predictive Control for Articulated Vehicle Stability With Experimental Validation

This article proposed a reconfigurable control scheme for articulated vehicles' stabilization by leveraging optimization-based control techniques. The central objective is to maintain a good lateral and yaw stability of the vehicle with optimal corrective brakes, meanwhile applicable to different actuation configurations. This is achieved by a two-layer control structure, where the high-level controller formulates as a model predictive control (MPC) tracking problem to generate corrective center-of-gravity (CG) yaw moment of each unit. The lower level controller utilizes the control allocation (CA) algorithm with real-time constraints to optimally calculate differential brakes at each wheel with maximum utilization-of-tires capacity. To evaluate its real-time performance, experimental validation is carried out on the electrified tractor-trailer with selective differential braking systems. It is observed that the controller is effective in dynamics control, meanwhile reconfigurable to various actuation configurations. Furthermore, the proposed system has great potential in production tractor-trailer systems due to the low cost and number of sensor requisites.

Multi-Objective Reconfigurable Three-Phase Off-Board Charger for EV

This paper deals with the control and implementation of solar photovoltaic (PV) array-based multi-objective bi-directional charger beneficial for electric vehicle (EV), household load, and utility. For EV, the charger provides the charging facility. For household load, the charger acts as a standalone inverter, and for utility the charger acts as an active power filter. However, for providing the multi-functionality and the multi-mode operation capability of the charger, a reconfigurable control strategy is proposed. Moreover, an adaptive dc-link voltage strategy is proposed for achieving the optimum voltage at dc link under all voltage conditions for achieving minimum ripple in grid currents. The charger also uses a voltage synchronization strategy for achieving the seamless mode transition between the grid-connected and standalone modes. In grid-connected mode, the charger uses a double second-order generalized integrator-based positive sequence estimator along with the improved linear sinusoidal tracer-based algorithm for generating the balanced and sinusoidal reference grid currents, under the unbalanced and distorted grid voltages. The charger is implemented in the laboratory, and the performance is presented under various steady-state and dynamic conditions.

Attitude Tracking Control Reconfiguration for Space Launch Vehicle With Thrust Loss Fault

The thrust loss fault of the space launch vehicle is quite different from that of ordinary actuator efficiency loss. Focusing on the attitude tracking control problem of the launch vehicle with thrust loss fault, the special impacts of that fault on the control system are explored, and a two-stage control reconfiguration strategy based on the cascaded pseudo-inverse allocation method and the neuron adaptive gain scheduling method is proposed for faults with different severity. Meanwhile, a practical reconfigurability analysis for the faulty system based on the control state reachability is presented for some representative fault scenarios. Based on the nonlinear dynamical model of the faulty system, lots of numerical simulations under various fault scenarios are finally carried out. The results indicate that the designed control reconfiguration strategy not only can effectively deal with the thrust loss fault with high practicability but also is easy to implement.

A Current-Mode Buck Converter With Reconfigurable On-Chip Compensation and Adaptive Voltage Positioning

Power management integrated circuits (PMICs) with on-chip compensation are widely used to power multiple loads in mobile devices with increased power density. However, there are two issues for on-chip compensated PMICs. First, on-chip compensation reconfigurability is required to obtain the appropriate response in various passive components. Second, a converter for a processor requires adaptive voltage positioning (AVP) to reduce the output capacitor size. In this paper, a novel reconfigurable on-chip compensated current-mode buck converter with AVP is proposed to solve the aforementioned issues without requiring high-speed and high-resolution analog-to-digital converter (ADC). A reconfigurable accurate load line control scheme and on-chip compensation are proposed to achieve an accurate load line and AVP in various load lines and passive components. The control scheme, small-signal model, and circuit implementation are illustrated in this paper. The proposed buck converter was implemented into an integrated circuit to verify the analysis.

A Reconfigurable Integrated Control for Narrow Tilting Vehicles

This paper proposes a reconfigurable control strategy for vehicles with tilting capabilities including a new rollover control approach. It can be applied to the emerging narrow tilting cars for urban transportation as well as conventional vehicles with semiactive or active suspensions. This paper extends the integrated lateral stability controller by considering the roll degrees of freedom for motion control. An envelope approach based on rollover index is proposed for the high-level controller of the vehicle to manage the rollover stability and the control energy consumption. The desired stabilizing forces are then distributed to available actuators using a reconfigurable optimal control allocation. The reconfigurable approach provides the freedom to select different actuators for the system without redesigning the controller. The optimal control allocation also ensures the feasibility as well as system robustness. It is shown via the simulation in CarSim that, by adopting the proposed control approach, tilting control effort is reduced and the vehicle handling, as well as stability in both lateral and roll motions, can be furthered improved.

Flight control reconfiguration of unmanned tiltrotor aircraft

The unmanned tiltrotor aircraft has many flying advantages, in the meantime it brings some new problems. In order to improve the flight stability of the UAV, the simulation of flight control law reconstruction was designed based on the multi-model adaptive control theory for actuator failure. Using the principle of small disturbance, the linear model of the UAV was established. Aiming at several typical actuator failures, the reconfigurable control strategy was designed. The classical PID control method was used to design the control law structure. Simulation results show that the proposed reconfiguration control strategy can be used in unmanned tiltrotor aircraft, which has good fault-tolerant effects and can significantly improve the safety of aircraft performance.

Dynamic gas kick regulation through control reconfiguration under MPD scenario – Two-phase flow validation

Controlling gas kick is essential to guarantee safe drilling of oil wells. As the gas flows toward the surface, its volume increases due to gas expansion, reducing mud weight. As a result, an uncontrolled gas kick may produce a blowout. A literature review, concerning MPD (Managed Pressure Drilling) technology, unveils that there is a gap regarding experimental validation of gas kick control strategies. Therefore, the main objective of this paper is building an experimental unit, representing the oil well drilling process, for dynamic gas kick control validation. Pressure, flow and level data are employed for real-time monitoring and control purposes. A drift-flux mathematical model (DFM) and a control reconfiguration scheme are validated using two-phase flow data from the experimental facility. The transient nature of the oil well drilling process, exhibiting a variety of operational modes and being nonlinear was successfully regulated by control reconfiguration, which works as an advanced control holistic structure.

Neural network–based reconfiguration control for spacecraft formation in obstacle environments

SummaryThis paper proposes an adaptive formation reconfiguration control scheme based on the leader‐follower strategy for multiple spacecraft systems. By taking the predesigned desired velocities and the trajectories as reference signals, a set of coordination tracking controllers is constructed by combining the reconstructed dynamic system and the neural network–based reconfiguration algorithm together. To avoid collisions between spacecraft and obstacles during the formation configuration process, the null space–based behavioral control is integrated into the control design. Since the spacecraft dynamics contains unknown nonlinearity and disturbance, it is challenging to make the system robust to uncertainties and improve the control precision simultaneously. To solve this problem, both the adaptive neural network strategy and the finite‐time control theory are employed. Finally, 2 simulation examples are carried out to verify the proposed algorithm, showing that the formation reconfiguration task can be executed successfully while achieving high control precision.

Data-Driven Reachability Analysis for the Reconfiguration of Vehicle Control Systems

The paper presents a reconfigurable control strategy for the lateral stability of autonomous vehicles. The control strategy is based on the analysis of big data, which are provided by the sensor networks of autonomous vehicles. The core of the analysis method is a machine learning algorithm, with which the impacts of various vehicle signals on the lateral dynamics have been examined. In the analysis several scenarios with faults in the steering and in-wheel systems are considered using a high-fidelity simulation software. The results of the examination are built into the fault-tolerant reconfiguration strategy.

An [formula omitted] cooperative fault recovery control of multi-agent systems

In this work, an H∞ performance fault recovery control problem for a team of multi-agent systems that is subject to actuator faults is studied. Our main objective is to design a distributed control reconfiguration strategy such that in presence of actuator faults, (a) the state consensus errors remain bounded, (b) the outputs of the faulty team behave exactly the same as that of the healthy team, and (c) the specified H∞ performance bound is guaranteed to be minimized in presence of bounded energy disturbances. The reconfigured control law gains are selected first by employing a geometric approach where a set of controllers guarantees that the output of the faulty agent imitates that of the healthy agent and that the consensus achievement objectives are satisfied. Next, the remaining degrees of freedom in selection of the control law gains are utilized to minimize the bound on a specified H∞ performance index. Finally, the effects of uncertainties and imperfections in the FDI module decision in estimating the fault severity are investigated and a bound on the maximum tolerable estimation uncertainties is obtained.

Distributed reconfigurable control strategies for switching topology networked multi-agent systems

In this paper, distributed control reconfiguration strategies for directed switching topology networked multi-agent systems are developed and investigated. The proposed control strategies are invoked when the agents are subject to actuator faults and while the available fault detection and isolation (FDI) modules provide inaccurate and unreliable information on the estimation of faults severities. Our proposed strategies will ensure that the agents reach a consensus while an upper bound on the team performance index is ensured and satisfied. Three types of actuator faults are considered, namely: the loss of effectiveness fault, the outage fault, and the stuck fault. By utilizing quadratic and convex hull (composite) Lyapunov functions, two cooperative and distributed recovery strategies are designed and provided to select the gains of the proposed control laws such that the team objectives are guaranteed. Our proposed reconfigurable control laws are applied to a team of autonomous underwater vehicles (AUVs) under directed switching topologies and subject to simultaneous actuator faults. Simulation results demonstrate the effectiveness of our proposed distributed reconfiguration control laws in compensating for the effects of sudden actuator faults and subject to fault diagnosis module uncertainties and unreliabilities.